Fix grammar

Doc/library/string.rst

@@ -729,9 +729,9 @@ placeholder syntax, delimiter character, or the entire regular expression used
 to parse template strings.  To do this, you can override these class attributes:
 
 * *delimiter* -- This is the literal string describing a placeholder introducing
-  delimiter.  The default value ``$``.  Note that this should *not* be a regular
-  expression, as the implementation will call :meth:`re.escape` on this string as
-  needed.
+  delimiter.  The default value is ``$``.  Note that this should *not* be a
+  regular expression, as the implementation will call :meth:`re.escape` on this
+  string as needed.
 
 * *idpattern* -- This is the regular expression describing the pattern for
   non-braced placeholders (the braces will be added automatically as